If all pets go to heaven, then i would like to imagine what they'd do about the few cougars and alligators and hippos some people keep, when they'd naturally try to kill the others, and whether that's allowed.. And fish..

I dont know if cats would naturally follow it. Many of their kills are for fun. Some days ago my cat caught a bird and just played around with it. They'll probably have to calm them down with catnip or something